765 lines
14 KiB
C
765 lines
14 KiB
C
/* Compute look-ahead criteria for bison,
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Copyright (C) 1984, 1986, 1989 Free Software Foundation, Inc.
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This file is part of Bison, the GNU Compiler Compiler.
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Bison is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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Bison is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with Bison; see the file COPYING. If not, write to
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the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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/* Compute how to make the finite state machine deterministic;
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find which rules need lookahead in each state, and which lookahead tokens they accept.
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lalr(), the entry point, builds these data structures:
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goto_map, from_state and to_state
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record each shift transition which accepts a variable (a nonterminal).
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ngotos is the number of such transitions.
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from_state[t] is the state number which a transition leads from
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and to_state[t] is the state number it leads to.
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All the transitions that accept a particular variable are grouped together and
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goto_map[i - ntokens] is the index in from_state and to_state of the first of them.
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consistent[s] is nonzero if no lookahead is needed to decide what to do in state s.
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LAruleno is a vector which records the rules that need lookahead in various states.
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The elements of LAruleno that apply to state s are those from
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lookaheads[s] through lookaheads[s+1]-1.
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Each element of LAruleno is a rule number.
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If lr is the length of LAruleno, then a number from 0 to lr-1
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can specify both a rule and a state where the rule might be applied.
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LA is a lr by ntokens matrix of bits.
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LA[l, i] is 1 if the rule LAruleno[l] is applicable in the appropriate state
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when the next token is symbol i.
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If LA[l, i] and LA[l, j] are both 1 for i != j, it is a conflict.
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*/
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#include <stdio.h>
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#include "system.h"
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#include "machine.h"
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#include "types.h"
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#include "state.h"
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#include "alloc.h"
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#include "gram.h"
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extern short **derives;
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extern char *nullable;
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int tokensetsize;
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short *lookaheads;
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short *LAruleno;
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unsigned *LA;
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short *accessing_symbol;
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char *consistent;
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core **state_table;
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shifts **shift_table;
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reductions **reduction_table;
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short *goto_map;
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short *from_state;
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short *to_state;
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void lalr PARAMS((void));
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short **transpose PARAMS((short **, int));
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void set_state_table PARAMS((void));
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void set_accessing_symbol PARAMS((void));
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void set_shift_table PARAMS((void));
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void set_reduction_table PARAMS((void));
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void set_maxrhs PARAMS((void));
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void initialize_LA PARAMS((void));
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void set_goto_map PARAMS((void));
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int map_goto PARAMS((int, int));
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void initialize_F PARAMS((void));
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void build_relations PARAMS((void));
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void add_lookback_edge PARAMS((int, int, int));
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void compute_FOLLOWS PARAMS((void));
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void compute_lookaheads PARAMS((void));
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void digraph PARAMS((short **));
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void traverse PARAMS((register int));
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extern void toomany PARAMS((char *));
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extern void berror PARAMS((char *));
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static int infinity;
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static int maxrhs;
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static int ngotos;
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static unsigned *F;
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static short **includes;
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static shorts **lookback;
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static short **R;
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static short *INDEX;
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static short *VERTICES;
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static int top;
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void
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lalr (void)
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{
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tokensetsize = WORDSIZE(ntokens);
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set_state_table();
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set_accessing_symbol();
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set_shift_table();
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set_reduction_table();
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set_maxrhs();
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initialize_LA();
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set_goto_map();
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initialize_F();
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build_relations();
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compute_FOLLOWS();
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compute_lookaheads();
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}
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void
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set_state_table (void)
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{
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register core *sp;
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state_table = NEW2(nstates, core *);
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for (sp = first_state; sp; sp = sp->next)
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state_table[sp->number] = sp;
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}
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void
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set_accessing_symbol (void)
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{
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register core *sp;
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accessing_symbol = NEW2(nstates, short);
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for (sp = first_state; sp; sp = sp->next)
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accessing_symbol[sp->number] = sp->accessing_symbol;
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}
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void
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set_shift_table (void)
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{
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register shifts *sp;
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shift_table = NEW2(nstates, shifts *);
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for (sp = first_shift; sp; sp = sp->next)
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shift_table[sp->number] = sp;
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}
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void
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set_reduction_table (void)
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{
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register reductions *rp;
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reduction_table = NEW2(nstates, reductions *);
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for (rp = first_reduction; rp; rp = rp->next)
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reduction_table[rp->number] = rp;
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}
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void
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set_maxrhs (void)
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{
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register short *itemp;
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register int length;
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register int max;
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length = 0;
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max = 0;
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for (itemp = ritem; *itemp; itemp++)
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{
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if (*itemp > 0)
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{
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length++;
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}
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else
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{
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if (length > max) max = length;
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length = 0;
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}
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}
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maxrhs = max;
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}
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void
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initialize_LA (void)
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{
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register int i;
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register int j;
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register int count;
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register reductions *rp;
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register shifts *sp;
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register short *np;
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consistent = NEW2(nstates, char);
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lookaheads = NEW2(nstates + 1, short);
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count = 0;
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for (i = 0; i < nstates; i++)
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{
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register int k;
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lookaheads[i] = count;
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rp = reduction_table[i];
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sp = shift_table[i];
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if (rp && (rp->nreds > 1
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|| (sp && ! ISVAR(accessing_symbol[sp->shifts[0]]))))
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count += rp->nreds;
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else
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consistent[i] = 1;
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if (sp)
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for (k = 0; k < sp->nshifts; k++)
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{
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if (accessing_symbol[sp->shifts[k]] == error_token_number)
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{
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consistent[i] = 0;
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break;
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}
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}
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}
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lookaheads[nstates] = count;
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if (count == 0)
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{
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LA = NEW2(1 * tokensetsize, unsigned);
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LAruleno = NEW2(1, short);
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lookback = NEW2(1, shorts *);
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}
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else
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{
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LA = NEW2(count * tokensetsize, unsigned);
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LAruleno = NEW2(count, short);
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lookback = NEW2(count, shorts *);
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}
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np = LAruleno;
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for (i = 0; i < nstates; i++)
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{
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if (!consistent[i])
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{
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if ((rp = reduction_table[i]))
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for (j = 0; j < rp->nreds; j++)
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*np++ = rp->rules[j];
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}
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}
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}
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void
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set_goto_map (void)
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{
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register shifts *sp;
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register int i;
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register int symbol;
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register int k;
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register short *temp_map;
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register int state2;
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register int state1;
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goto_map = NEW2(nvars + 1, short) - ntokens;
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temp_map = NEW2(nvars + 1, short) - ntokens;
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ngotos = 0;
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for (sp = first_shift; sp; sp = sp->next)
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{
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for (i = sp->nshifts - 1; i >= 0; i--)
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{
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symbol = accessing_symbol[sp->shifts[i]];
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if (ISTOKEN(symbol)) break;
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if (ngotos == MAXSHORT)
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toomany(_("gotos"));
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ngotos++;
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goto_map[symbol]++;
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}
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}
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k = 0;
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for (i = ntokens; i < nsyms; i++)
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{
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temp_map[i] = k;
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k += goto_map[i];
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}
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for (i = ntokens; i < nsyms; i++)
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goto_map[i] = temp_map[i];
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goto_map[nsyms] = ngotos;
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temp_map[nsyms] = ngotos;
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from_state = NEW2(ngotos, short);
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to_state = NEW2(ngotos, short);
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for (sp = first_shift; sp; sp = sp->next)
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{
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state1 = sp->number;
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for (i = sp->nshifts - 1; i >= 0; i--)
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{
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state2 = sp->shifts[i];
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symbol = accessing_symbol[state2];
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if (ISTOKEN(symbol)) break;
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k = temp_map[symbol]++;
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from_state[k] = state1;
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to_state[k] = state2;
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}
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}
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FREE(temp_map + ntokens);
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}
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/* Map_goto maps a state/symbol pair into its numeric representation. */
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int
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map_goto (int state, int symbol)
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{
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register int high;
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register int low;
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register int middle;
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register int s;
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low = goto_map[symbol];
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high = goto_map[symbol + 1] - 1;
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while (low <= high)
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{
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middle = (low + high) / 2;
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s = from_state[middle];
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if (s == state)
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return (middle);
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else if (s < state)
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low = middle + 1;
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else
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high = middle - 1;
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}
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berror("map_goto");
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/* NOTREACHED */
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return 0;
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}
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void
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initialize_F (void)
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{
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register int i;
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register int j;
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register int k;
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register shifts *sp;
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register short *edge;
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register unsigned *rowp;
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register short *rp;
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register short **reads;
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register int nedges;
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register int stateno;
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register int symbol;
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register int nwords;
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nwords = ngotos * tokensetsize;
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F = NEW2(nwords, unsigned);
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reads = NEW2(ngotos, short *);
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edge = NEW2(ngotos + 1, short);
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nedges = 0;
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rowp = F;
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for (i = 0; i < ngotos; i++)
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{
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stateno = to_state[i];
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sp = shift_table[stateno];
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if (sp)
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{
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k = sp->nshifts;
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for (j = 0; j < k; j++)
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{
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symbol = accessing_symbol[sp->shifts[j]];
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if (ISVAR(symbol))
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break;
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SETBIT(rowp, symbol);
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}
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for (; j < k; j++)
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{
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symbol = accessing_symbol[sp->shifts[j]];
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if (nullable[symbol])
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edge[nedges++] = map_goto(stateno, symbol);
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}
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if (nedges)
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{
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reads[i] = rp = NEW2(nedges + 1, short);
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for (j = 0; j < nedges; j++)
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rp[j] = edge[j];
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rp[nedges] = -1;
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nedges = 0;
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}
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}
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rowp += tokensetsize;
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}
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digraph(reads);
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for (i = 0; i < ngotos; i++)
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{
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if (reads[i])
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FREE(reads[i]);
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}
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FREE(reads);
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FREE(edge);
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}
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void
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build_relations (void)
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{
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register int i;
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register int j;
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register int k;
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register short *rulep;
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register short *rp;
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register shifts *sp;
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register int length;
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register int nedges;
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register int done;
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register int state1;
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register int stateno;
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register int symbol1;
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register int symbol2;
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register short *shortp;
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register short *edge;
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register short *states;
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register short **new_includes;
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includes = NEW2(ngotos, short *);
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edge = NEW2(ngotos + 1, short);
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states = NEW2(maxrhs + 1, short);
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for (i = 0; i < ngotos; i++)
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{
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nedges = 0;
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state1 = from_state[i];
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symbol1 = accessing_symbol[to_state[i]];
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for (rulep = derives[symbol1]; *rulep > 0; rulep++)
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{
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length = 1;
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states[0] = state1;
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stateno = state1;
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for (rp = ritem + rrhs[*rulep]; *rp > 0; rp++)
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{
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symbol2 = *rp;
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sp = shift_table[stateno];
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k = sp->nshifts;
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for (j = 0; j < k; j++)
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{
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stateno = sp->shifts[j];
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if (accessing_symbol[stateno] == symbol2) break;
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}
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states[length++] = stateno;
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}
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if (!consistent[stateno])
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add_lookback_edge(stateno, *rulep, i);
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length--;
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done = 0;
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while (!done)
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{
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done = 1;
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rp--;
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/* JF added rp>=ritem && I hope to god its right! */
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if (rp>=ritem && ISVAR(*rp))
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{
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stateno = states[--length];
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edge[nedges++] = map_goto(stateno, *rp);
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if (nullable[*rp]) done = 0;
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}
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}
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}
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if (nedges)
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{
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includes[i] = shortp = NEW2(nedges + 1, short);
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for (j = 0; j < nedges; j++)
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shortp[j] = edge[j];
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shortp[nedges] = -1;
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}
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}
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new_includes = transpose(includes, ngotos);
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for (i = 0; i < ngotos; i++)
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if (includes[i])
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FREE(includes[i]);
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FREE(includes);
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includes = new_includes;
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FREE(edge);
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FREE(states);
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}
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void
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add_lookback_edge (int stateno, int ruleno, int gotono)
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{
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register int i;
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register int k;
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register int found;
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register shorts *sp;
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i = lookaheads[stateno];
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k = lookaheads[stateno + 1];
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found = 0;
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while (!found && i < k)
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{
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if (LAruleno[i] == ruleno)
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found = 1;
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else
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i++;
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}
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if (found == 0)
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berror("add_lookback_edge");
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sp = NEW(shorts);
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sp->next = lookback[i];
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sp->value = gotono;
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lookback[i] = sp;
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}
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short **
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transpose (short **R_arg, int n)
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{
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register short **new_R;
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register short **temp_R;
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register short *nedges;
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register short *sp;
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register int i;
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register int k;
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nedges = NEW2(n, short);
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for (i = 0; i < n; i++)
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{
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sp = R_arg[i];
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if (sp)
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{
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while (*sp >= 0)
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nedges[*sp++]++;
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}
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}
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new_R = NEW2(n, short *);
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temp_R = NEW2(n, short *);
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for (i = 0; i < n; i++)
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{
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k = nedges[i];
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if (k > 0)
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{
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sp = NEW2(k + 1, short);
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new_R[i] = sp;
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temp_R[i] = sp;
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sp[k] = -1;
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}
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}
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FREE(nedges);
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for (i = 0; i < n; i++)
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{
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sp = R_arg[i];
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if (sp)
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{
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while (*sp >= 0)
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*temp_R[*sp++]++ = i;
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}
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|
}
|
|
|
|
FREE(temp_R);
|
|
|
|
return (new_R);
|
|
}
|
|
|
|
|
|
void
|
|
compute_FOLLOWS (void)
|
|
{
|
|
register int i;
|
|
|
|
digraph(includes);
|
|
|
|
for (i = 0; i < ngotos; i++)
|
|
{
|
|
if (includes[i]) FREE(includes[i]);
|
|
}
|
|
|
|
FREE(includes);
|
|
}
|
|
|
|
|
|
void
|
|
compute_lookaheads (void)
|
|
{
|
|
register int i;
|
|
register int n;
|
|
register unsigned *fp1;
|
|
register unsigned *fp2;
|
|
register unsigned *fp3;
|
|
register shorts *sp;
|
|
register unsigned *rowp;
|
|
/* register short *rulep; JF unused */
|
|
/* register int count; JF unused */
|
|
register shorts *sptmp;/* JF */
|
|
|
|
rowp = LA;
|
|
n = lookaheads[nstates];
|
|
for (i = 0; i < n; i++)
|
|
{
|
|
fp3 = rowp + tokensetsize;
|
|
for (sp = lookback[i]; sp; sp = sp->next)
|
|
{
|
|
fp1 = rowp;
|
|
fp2 = F + tokensetsize * sp->value;
|
|
while (fp1 < fp3)
|
|
*fp1++ |= *fp2++;
|
|
}
|
|
|
|
rowp = fp3;
|
|
}
|
|
|
|
for (i = 0; i < n; i++)
|
|
{/* JF removed ref to freed storage */
|
|
for (sp = lookback[i]; sp; sp = sptmp) {
|
|
sptmp=sp->next;
|
|
FREE(sp);
|
|
}
|
|
}
|
|
|
|
FREE(lookback);
|
|
FREE(F);
|
|
}
|
|
|
|
|
|
void
|
|
digraph (short **relation)
|
|
{
|
|
register int i;
|
|
|
|
infinity = ngotos + 2;
|
|
INDEX = NEW2(ngotos + 1, short);
|
|
VERTICES = NEW2(ngotos + 1, short);
|
|
top = 0;
|
|
|
|
R = relation;
|
|
|
|
for (i = 0; i < ngotos; i++)
|
|
INDEX[i] = 0;
|
|
|
|
for (i = 0; i < ngotos; i++)
|
|
{
|
|
if (INDEX[i] == 0 && R[i])
|
|
traverse(i);
|
|
}
|
|
|
|
FREE(INDEX);
|
|
FREE(VERTICES);
|
|
}
|
|
|
|
|
|
void
|
|
traverse (register int i)
|
|
{
|
|
register unsigned *fp1;
|
|
register unsigned *fp2;
|
|
register unsigned *fp3;
|
|
register int j;
|
|
register short *rp;
|
|
|
|
int height;
|
|
unsigned *base;
|
|
|
|
VERTICES[++top] = i;
|
|
INDEX[i] = height = top;
|
|
|
|
base = F + i * tokensetsize;
|
|
fp3 = base + tokensetsize;
|
|
|
|
rp = R[i];
|
|
if (rp)
|
|
{
|
|
while ((j = *rp++) >= 0)
|
|
{
|
|
if (INDEX[j] == 0)
|
|
traverse(j);
|
|
|
|
if (INDEX[i] > INDEX[j])
|
|
INDEX[i] = INDEX[j];
|
|
|
|
fp1 = base;
|
|
fp2 = F + j * tokensetsize;
|
|
|
|
while (fp1 < fp3)
|
|
*fp1++ |= *fp2++;
|
|
}
|
|
}
|
|
|
|
if (INDEX[i] == height)
|
|
{
|
|
for (;;)
|
|
{
|
|
j = VERTICES[top--];
|
|
INDEX[j] = infinity;
|
|
|
|
if (i == j)
|
|
break;
|
|
|
|
fp1 = base;
|
|
fp2 = F + j * tokensetsize;
|
|
|
|
while (fp1 < fp3)
|
|
*fp2++ = *fp1++;
|
|
}
|
|
}
|
|
}
|